Calculating fluid distribution in subterranean reservoirs is one approach to determining whether a given reservoir is a potential hydrocarbon reserve. As hydrocarbon exploration and production moves to methods of enhanced oil recovery and methods that utilize unconventional reservoirs such as complex carbonate formations and shale gas formations, the calculation of the fluid distribution can become more difficult in formations containing heterogeneous rock types and variations in porosity.
One method of characterizing fluid distributions within a formation includes the volumetric calculation of the hydrocarbons in place using a water saturation-height function. Water saturation-height functions can be determined using porosity data and water saturation values from well logs and/or core sample characterization. However, in some formations, variations in pore geometry may negatively affect the predictability of petrophysical properties using such techniques, particularly where the saturation-height functions assume a homogenous formation having little or no variability of pore size or pore connectivity.